The 1991 Bluebird/RCA set is very good. It's available used and in very good condition at Amazon Marketplace for ninety bucks. The MP3 version is $45. The standard MP3 files are 256 kbps, which is plenty for my less-than-perfect hearing. I can't believe you will get better sound from a lossless MP3 of a 1940 recording, but maybe I'm wrong.

-Joe-